#4258 προαμαρτάνω proamartano {pro-am-ar-tan'-o}

 from G4253 and G0264; TDNT - n/a; v

—Greek Word Study (Transliteration-Pronunciation Etymology & Grammar)

 1) to sin before
    1a) of those who before receiving baptism had been guilty of the
        vices especially common among the Gentiles

—Thayer's (New Testament Greek-English Lexicon)

—Strong's (Greek Dictionary of the New Testament)

—NAS Exhaustive Concordance of the Bible with Hebrew-Aramaic and Greek Dictionaries

 AV - sin already 1, sin heretofore 1; 2

—Exhaustive Concordance (KJV Translation Frequency & Location)